Helma B. Wennemers (born 24 June 1969 in Offenbach am Main) is a German organic chemist. She is a professor of organic chemistry at the Swiss Federal Institute of Technology in Zurich (ETH Zurich).
Helma B. Wennemers (born 24 June 1969 in Offenbach am Main) is a German organic chemist. She is a professor of organic chemistry at the Swiss Federal Institute of Technology in Zurich (ETH Zurich).
Helma Wennemers studied chemistry at the Goethe University Frankfurt, completing her diploma thesis with Gerhard Quinkert in 1993. She earned her PhD at Columbia University, New York in 1996, under the supervision of W. Clark Still, with a thesis "Encoded combinatorial chemistry: a tool for the study of selective intermolecular interactions." Between 1996 and 1998, she was a postdoctoral fellow at Nagoya University with Hisashi Yamamoto, before being appointed Bachem Assistant Professor at the University of Basel in 1999. She held this post until 2003, where she was promoted to associate professor. In 2011, she moved to ETH Zurich as a professor of organic chemistry.
Wennemers' research focuses on proline-rich peptides.
Wennemers led the development of tripeptides containing H-Pro-Pro-Xaa type sequences (Pro: proline, Xaa: any amine) as organocatalysts for C–C bond formations based on an enamine mechanism. [1] High reactivity, stereo- and chemoselectivity for aldol [2] or conjugate addition reactions [3] [4] can be achieved by varying the absolute configuration of the single amino acids as well as the functional group of the Xaa residue. The modularity of the peptides enabled creation of catalysts capable of catalyzing the conjugate addition reactions of aldehydes to nitroolefins with as little as 0.05 mol% of tripeptidic catalyst. [5]
She also worked on other organocatalyzed transformations. Inspired by natural polyketide synthases—which use malonic acid half thioesters (MAHTs) as thioester enolate equivalents — she developed organocatalytic methods for stereoselective addition reactions of MAHTs (and protected variants monothiomalonates, MTMs) to electrophiles using cinchona alkaloid derived catalysts. The introduction of fluorinated MAHTs and MTMs allowed for the stereoselective introduction of fluorine substituents in fluoroacetate aldol reactions [6] as well as further addition reactions to imines [7] and nitroolefins. [8]
In chemical biology, Wennemers uses larger proline-rich peptides, such as collagen model peptides or oligoprolines, for applications such as tumor targeting, [9] cell penetration [10] or drug delivery. She utilized Cγ-functionalized proline derivatives for the functionalization and stabilization of short-chained collagen triple helices. Further, she introduced aminoproline [11] and γ-azaproline [12] as pH-sensitive probes to tune the conformational stability of the collagen triple helix by pH change. In the field of cell penetrating peptides (CPPs), Wennemers showed that preorganization of cationic charges along an oligoproline backbone enhanced the cellular uptake of CPPs compared to more flexible oligoarginines with undefined charge display. [10] Moreover, the oligoproline-based CPPs demonstrated a defined nuclear localization and high proteolytic stability as well as low cytotoxicity.
Wennemers utilizes peptides to control the morphology of nanostructured materials for generation of ordered mesoscopic materials. She developed tripeptides for the size-controlled generation of mono-disperse, water-soluble silver-, palladium-, platinum-, and gold nanoparticles. [13] Recently, she reported peptide‐stabilized platinum nanoparticles that have greater toxicity against hepatic cancer cells (HepG2) than against other cancer cells and non‐cancerous liver cells. [14] Wennemers also explored conjugates of oligoprolines and π-conjugated systems that form hierarchical self-assemblies with diverse morphologies (e.g. nanofibers, nanorods, nanosheets). She used such a conjugate to prepare the first example of an extended triaxial supramolecular weave held together through the interplay of weak non-covalent interactions. [15]
Wennemers work was recognized by the Leonidas Zervas Award of the European Peptide Society (2010), [16] the Pedler Award of the Royal Society of Chemistry (2016), [17] the Inhoffen Medal (2017), [18] the Netherlands Scholar Award for Supramolecular Chemistry (2019) [19] and the Arthur C. Cope Scholar Award (2020). [20]
The aldol reaction is a reaction that combines two carbonyl compounds to form a new β-hydroxy carbonyl compound.
In organic chemistry, the Michael reaction or Michael 1,4 addition is a reaction between a Michael donor and a Michael acceptor to produce a Michael adduct by creating a carbon-carbon bond at the acceptor's β-carbon. It belongs to the larger class of conjugate additions and is widely used for the mild formation of carbon-carbon bonds.
In organic chemistry, organocatalysis is a form of catalysis in which the rate of a chemical reaction is increased by an organic catalyst. This "organocatalyst" consists of carbon, hydrogen, sulfur and other nonmetal elements found in organic compounds. Because of their similarity in composition and description, they are often mistaken as a misnomer for enzymes due to their comparable effects on reaction rates and forms of catalysis involved.
The Hajos–Parrish–Eder–Sauer–Wiechert reaction in organic chemistry is a proline catalysed asymmetric aldol reaction. The reaction is named after the principal investigators of the two groups who reported it simultaneously: Zoltan Hajos and David Parrish from Hoffmann-La Roche and Rudolf Wiechert and co-workers from Schering AG. Discovered in the 1970s the original Hajos-Parrish catalytic procedure – shown in the reaction equation, leading to the optically active bicyclic ketol – paved the way of asymmetric organocatalysis. The Eder-Sauer-Wiechert modification lead directly to the optically active enedione, through the loss of water from the bicyclic ketol shown in figure.
Alexander C. Filippou has been a Professor of Inorganic Chemistry at the Rheinische-Friedrich-Wilhelms-University Bonn since 2005.
Within the area of organocatalysis, (thio)urea organocatalysis describes the use of ureas and thioureas to accelerate and stereochemically alter organic transformations. The effects arise through hydrogen-bonding interactions between the substrate and the (thio)urea. Unlike classical catalysts, these organocatalysts interact by non-covalent interactions, especially hydrogen bonding. The scope of these small-molecule H-bond donors termed (thio)urea organocatalysis covers both non-stereoselective and stereoselective applications.
Ulrich "Uli" Kortz is a German chemist and professor, working in the area of synthetic polyoxometalate chemistry.
Proline organocatalysis is the use of proline as an organocatalyst in organic chemistry. This theme is often considered the starting point for the area of organocatalysis, even though early discoveries went unappreciated. Modifications, such as MacMillan’s catalyst and Jorgensen's catalysts, proceed with excellent stereocontrol.
Corinna S. Schindler is a Professor of Chemistry at the University of Michigan. She develops catalytic reactions with environmentally benign metals such as iron, towards the synthesis of biologically active small molecules. For her research in the development of new catalysts, Schindler has been honored with several early-career researcher awards including the David and Lucile Packard Foundation Fellowship in 2016, the Alfred P. Sloan Fellowship in 2017, and being named a member of the C&EN Talented 12 in 2017. Schindler has served on the Editorial Board of Organic and Bimolecular Chemistry since 2018.
Vy Maria Dong is a Vietnamese-American Professor of Chemistry at the University of California, Irvine (UCI). Dong works on enantioselective catalysis and natural product synthesis. She received the Royal Society of Chemistry's Merck, Sharp & Dohme Award in 2020, the American Chemical Society's Elias James Corey Award in 2019, and the UCI's Distinguished Alumni Award in 2018.
Richard Dronskowski is a German chemist and physicist. He is a full professor at the RWTH Aachen University.
Paul Knochel is a French chemist and a member of the French Academy of Sciences.
1,4-Dicyanobenzene is an organic compound with the formula C6H4(CN)2. Two other isomers exist, phthalonitrile and isophthalonitrile. All three isomers are produced commercially by ammoxidation of the corresponding xylene isomers. 1,4-Dicyanobenzene is a colorless or white solid with low solubility in water. Hydrogenation of isophthalonitrile affords p-xylylenediamine.
Katrina Anne Jolliffe is an Australian supramolecular and organic chemist and professor at the University of Sydney.
Regina Palkovits is a German chemist who is a Professor of Chemistry at the RWTH Aachen University. Her research considers heterogenous catalysis. She was elected a Fellow of the North Rhine-Westphalian Academy of Sciences, Humanities and the Arts in 2020.
The nitro-Mannich reaction is the nucleophilic addition of a nitroalkane to an imine, resulting in the formation of a beta-nitroamine. With the reaction involving the addition of an acidic carbon nucleophile to a carbon-heteroatom double bond, the nitro-Mannich reaction is related to some of the most fundamental carbon-carbon bond forming reactions in organic chemistry, including the aldol reaction, Henry reaction and Mannich reaction.
Benjamin List is a German chemist who is one of the directors of the Max Planck Institute for Coal Research and professor of organic chemistry at the University of Cologne. He co-developed organocatalysis, a method of accelerating chemical reactions and making them more efficient. He shared the 2021 Nobel Prize in Chemistry with David MacMillan "for the development of asymmetric organocatalysis".
The ketimine Mannich reaction is an asymmetric synthetic technique using differences in starting material to push a Mannich reaction to create an enantiomeric product with steric and electronic effects, through the creation of a ketimine group. Typically, this is done with a reaction with proline or another nitrogen-containing heterocycle, which control chirality with that of the catalyst. This has been theorized to be caused by the restriction of undesired (E)-isomer by preventing the ketone from accessing non-reactive tautomers. Generally, a Mannich reaction is the combination of an amine, a ketone with a β-acidic proton and aldehyde to create a condensed product in a β-addition to the ketone. This occurs through an attack on the ketone with a suitable catalytic-amine unto its electron-starved carbon, from which an imine is created. This then undergoes electrophilic addition with a compound containing an acidic proton. It is theoretically possible for either of the carbonyl-containing molecules to create diastereomers, but with the addition of catalysts which restrict addition as of the enamine creation, it is possible to extract a single product with limited purification steps and in some cases as reported by List et al.; practical one-pot syntheses are possible. The process of selecting a carbonyl-group gives the reaction a direct versus indirect distinction, wherein the latter case represents pre-formed products restricting the reaction's pathway and the other does not. Ketimines selects a reaction group, and circumvent a requirement for indirect pathways.
Alison Wendlandt is an American chemist who is an assistant professor at the Massachusetts Institute of Technology. Her research considers the development of catalysts for organic synthesis.
René Peters is a German chemist and since 2008 Professor of Organic Chemistry at the University of Stuttgart.
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